Field of the invention
The invention herein disclosed relates broadly to a new and improved thread milling cutter assembly where worn out carbide blades can be readily replaced with new replacement blades to avoid the expense of replacing the entire tool so as to minimize replacement costs.
As another feature, the holder is uniquely configurated to enable blades to be securely attached to a blade or tool holder in such a manner so as to allow screw threads to be milled in a very accurate manner.
According to more specific features of our invention, we have developed a new carbide tool where we are now able to change the thread form at the machine site and still maintain the accuracy needed to produce a quality thread. The user is also able to replace worn or broken blades very easily, because of our new and improved construction of the holder. The leading edge of the tool is cut in or machined under extreme accuracy so as to maintain lateral and central positioning for locating the vertical and also for locating the serrations.
According to our invention, it is important that a proper relationship be maintained between the blades and the serrations, and to maintain proper diameter through the use of jig ground pins. These pins are put in under high accuracy in relationship to the centerline of the tool and also the centerline of the pins. The location from the bottom edge of the tool and the centerline of the leading pin is also maintained under extreme accuracy for blade location.
Now for the carbide blade, two 45 degree slots are form ground at one time to insure location of centerline points of cutting blade and its cutting edge or serrations or V. Then a 2 degree back taper is ground on the back side of the carbide blade. The back taper enables the wedge to hold the blade down on the pins. From that point the blade serrations or cutting edges are then ground off of 45 degree grooves or V-shaped notches to insure proper location height of the cutting edges. After the blade is put into the holder and is rested on the pins, a wedge is installed.
The wedge is ground as to put pressure against the carbide blade in two ways. The first way is to hold the bit or blade against the leading edge of the holder which is very crucial. The second way is designed to hold the blade down on the pins, and this is done with a 2 degree front taper on the wedge, and a 30 degree back taper pushes the tool forward against the leading edge. This is all held together by three 0.160" diameter screws which put and maintain pressure against the wedge. To change the blade, you merely loosen the three screws and slide the blade on the bottom and reverse the process to install new blades. All the blades may be purchased at a fraction of the cost of a new tool with no difference in quality of tooling. Also, our new construction enables the user to change thread pitches just by changing the blades. The tool can be utilized in setups for vertical or horizontal machining centers.